1. Field of the Invention
This invention generally relates to data storage devices and more particularly to a fixed disk drive system employing a plurality of hard disks carrying magnetically stored data in magnetic media on the disk surfaces and a plurality of rotatable head positioning actuator assemblies.
2. Description of the Related Art
Fixed disk data storage devices typically are magnetic disk devices which utilize a head disk assembly enclosed within a sealed volume with its associated electronics circuitry located adjacent, above or below the sealed head disk assembly or "IDA". The head disk assembly typically includes one or more planar disks stacked on a rotating hub of an included spindle drive motor. Each disk has a magnetic media on its upper and lower surfaces. One or more actuator assemblies for positioning magnetic transducers (heads) over the upper and lower surfaces of the disks is positioned adjacent the stack of disks and includes a rotary motor means such as a voice coil motor for rotating arms, which carry the heads, back and forth over the disk surfaces in order to read and write information from and to the disks.
Main frame computers, high-end file servers, and high performance work stations all require high capacity and extremely high data transfer rates between the computers and data storage devices such as tape drives, hard disk drives or storage modules.
Rotating media storage systems require a certain finite time interval for the read/write head positioning actuator to seek and position the heads accurately over each particular data track. Therefore, there are two general data retrieval schemes in use. The first is serial transfer. In the serial transfer scheme, the actuator first positions the read/write heads over a particular track, data is then read or written with one head at a time in serial by bit mode, then the data stream is interrupted while the actuator moves the heads to a new track location. The second scheme is parallel computing transfer. The parallel computing scheme typically requires two or more separate storage modules, each having a separate head/actuator assembly so that one actuator may seek a new data location while the other actuator is retrieving or writing data. Data is read or written with eight heads simultaneously in parallel by byte mode. The overall data transfer rate is much faster in parallel computing since data transfer does not have to be halted while the actuator seeks out the desired track as is the case with serial transfer.
With the current trend of main frame computer technology and high end file servers to smaller and smaller size, and the concurrent demand for more and more storage space in the lower end machines, there remains an ever increasing need for more data storage capacity in a standard given volume. This is also true in high performance storage systems. However, there are physical limits on the availability of such space. For example, most desktop and tower file servers and personal computer cases are sized to receive peripheral components having a 51/4 inch form factor or smaller.
Most of the conventional disk drives available today contain a single stack of disks and a single voice coil motor operated actuator assembly which utilizes a moving coil attached to the actuator itself. The actuator has the same number of heads as surfaces on the disks. However, the inner actuator arms typically carry two opposing heads, one for the lower surface of the disk immediately above and one for the upper surface of the immediately adjacent lower disk.
There have been a number of attempts to increase the capacity of hard disk drives. One approach has been to reduce the distance between disks so that more disks may be installed in a given height drive. This can be done, for example, by making the disks thinner, making the actuator arms and heads thinner, and/or by providing side-by-side heads on the intermediate actuator arms. Examples of the latter approach are disclosed in U.S. Pat. No. 5,218,496 to Kaczeus and in my U.S. Pat. No. 5,343,345.
One can also provide multiple actuator assemblies in the HDA with each being operable on one set of surfaces, i.e., "volume", of the stack of disks. An example of this approach is provided in my U.S. Pat. No. 5,343,347. Another approach is to provide multiple actuators and multiple sets of heads to simultaneously access different areas of the disks. Some examples of this approach are provided in my U.S. Pat. No. 5,343,347 and U.S. Pat. No. 5,223,993.
The assembly methods conventionally used are complex, cumbersome and prone to error and therefore require meticulous attention to detail. For example, the actuators are typically machine formed from a single block of metal, such as aluminum or magnesium, into an "E-block" shape. In other words, the actuator has a cylindrical body portion with a plurality of radially and parallel projecting arms extending at a given angle from the body portion. The cylindrical body portion typically has a central axial bore for receiving a top and bottom bearing assembly therein. The cylindrical body portion rotatably mounted on a stationary spindle mounted to a baseplate via these bearing assemblies. The E-block also typically carries a voice coil motor coil typically extending in a direction opposite that of the arms. This coil fits between a pair of stationary permanent magnet sets mounted in the drive housing so that the actuator coil is free to rotate back and forth in the space between the magnet sets through a limited arc. The coil mass offsets the head arm mass thus the actuator is balanced. Current fed through the voice coil produces a reactive torque on the actuator commensurate with the magnitude and direction of current to rotate the actuator to and from a desired position.
Each actuator arm carries either one or two gimbal mounted read/write heads. The heads are carried at one end of a flexure. The other end of the flexure is ball staked to the actuator arm. The flexure with a head mounted thereto is often called a "head gimbal assembly" or "HGA". Conventional actuator arms of the E-block are joined with their head gimbal assemblies by staking all of the HGAs to their respective arms in a single operation. For example, an actuator E-block having 8 actuator arms has to have 14 HGAs held in position on the ends of the arms while a metal ball is shot through the matched aligning holes in the ends of the HGAs and through the ends of the E-block actuator arms. Passage of the ball spreads the metal of the flexure against the walls of the holes in the actuator arms to stake the HGAs in place. This staking operation is extremely prone to error. Error rates increase as the number of actuator areas of the E-block increases. It is extremely difficult to ensure that each of the HGAs is securely fastened to its actuator arm with this method. In addition, if one of the HGAs is not securely fastened to its actuator arm of the E-block, the entire E-block with 14 heads (HGAs) could be discarded. This can get very expensive. Therefore, there is a need for a more uniform assembly technique of HGAs to actuator arms that reduces the likelihood and consequence of defects in manufacturing and assembly.
Another problem with current hard disk drive construction techniques is that although the stack of hard disks is sequentially assembled on the drive motor hub, the actuator is separately assembled as a unit apart from the disk stack with all of the HGAs attached to the actuator arms. A spreader comb must then be inserted between the HGAs to allow the arms and HGAs to be inserted as a unit with the arms between the stacked disks. The comb is then removed and the actuator assembly installed or fastened to the frame of the drive apparatus. With present head and disk media assembly technology the release of the heads from the comb has to occur in the inner diameter of the disk. This operation is extremely delicate and often results in failed heads due to misalignment problems during installation.
Fixed disk data storage devices typically are magnetic disk devices which utilize a head disk assembly enclosed within a sealed volume with its associated electronics circuitry located adjacent, above or below the sealed head disk assembly or "HDA". The head disk assembly typically includes one or more planar disks stacked on a rotating hub of an included spindle drive motor. Each disk has a magnetic media on its upper and lower surfaces. One or more actuator assemblies for positioning magnetic transducers (heads) over the upper and lower surfaces of the disks is positioned adjacent the stack of disks and includes a rotary motor means such as a voice coil motor for rotating arms, which carry the heads, back and forth over the disk surfaces in order to read and write information from and to the disks.
Main frame computers, high-end file servers, and high performance work stations all require high capacity and extremely high data transfer rates between the computers and data storage devices such as tape drives, hard disk drives or storage modules.
Rotating media storage systems require a certain finite time interval for the read/write head positioning actuator to seek and position the heads accurately over each particular data track. Therefore, there are two general data retrieval schemes in use. The first is serial transfer. In the serial transfer scheme, the actuator first positions the read/write heads over a particular track, data is then read or written with one head at a time in serial by bit mode, then the data stream is interrupted while the actuator moves the heads to a new track location. The second scheme is parallel computing transfer. The parallel computing scheme typically requires two or more separate storage modules, each having a separate head/actuator assembly so that one actuator may seek a new data location while the other actuator is retrieving or writing data. Data is read or written with eight heads simultaneously in parallel by byte mode. The overall data transfer rate is much faster in parallel computing since data transfer does not have to be halted while the actuator seeks out the desired track as is the case with serial transfer.
With the current trend of main frame computer technology and high end file servers to smaller and smaller size, and the concurrent demand for more and more storage space in the lower end machines, there remains an ever increasing need for more data storage capacity in a standard given volume. This is also true in high performance storage systems. However, there are physical limits on the availability of such space. For example, most desktop and tower file servers and personal computer cases are sized to receive peripheral components having a 51/4 inch form factor or smaller.
Most of the conventional disk drives available today contain a single stack of disks and a single voice coil motor operated actuator assembly which utilizes a moving coil attached to the actuator itself. The actuator has the same number of heads as surfaces on the disks. However, the inner actuator arms typically carry two opposing heads, one for the lower surface of the disk immediately above and one for the upper surface of the immediately adjacent lower disk.
There have been a number of attempts to increase the capacity of hard disk drives. One approach has been to reduce the distance between disks so that more disks may be installed in a given height drive. This can be done, for example, by making the disks thinner, making the actuator arms and heads thinner, and/or by providing side-by-side heads on the intermediate actuator arms. Examples of the latter approach are disclosed in U.S. Pat. No. 5,218,496 to Kaczeus and in my U.S. Pat. No. 5,343,345.
One can also provide multiple actuator assemblies in the HDA with each being operable on one set of surfaces, i.e., "volume", of the stack of disks. An example of this approach is provided in my U.S. Pat. No. 5,343,347. Another approach is to provide multiple actuators and multiple sets of heads to simultaneously access different areas of the disks. Some examples of this approach are provided in my U.S. Pat. No. 5,343,347 and U.S. Pat. No. 5,223,993.
The assembly methods conventionally used are complex, cumbersome and prone to error and therefore require meticulous attention to detail. For example, the actuators are typically machine formed from a single block of metal, such as aluminum or magnesium, into an "E-block" shape. In other words, the actuator has a cylindrical body portion with a plurality of radially and parallel projecting arms extending at a given angle from the body portion. The cylindrical body portion typically has a central axial bore for receiving a top and bottom bearing assembly therein. The cylindrical body portion rotatably mounted on a stationary spindle mounted to a baseplate via these bearing assemblies. The E-block also typically carries a voice coil motor coil typically extending in a direction opposite that of the arms. This coil fits between a pair of stationary permanent magnet sets mounted in the drive housing so that the actuator coil is free to rotate back and forth in the space between the magnet sets through a limited arc. The coil mass offsets the head arm mass thus the actuator is balanced. Current fed through the voice coil produces a reactive torque on the actuator commensurate with the magnitude and direction of current to rotate the actuator to and from a desired position.
Each actuator arm carries either one or two gimbal mounted read/write heads. The heads are carried at one end of a flexure. The other end of the flexure is ball staked to the actuator arm. The flexure with a head mounted thereto is often called a "head gimbal assembly" or "HGA". Conventional actuator arms of the E-block are joined with their head gimbal assemblies by staking all of the HGAs to their respective arms in a single operation. For example, an actuator E-block having 8 actuator arms has to have 14 HGAs held in position on the ends of the arms while a metal ball is shot through the matched aligning holes in the ends of the HGAs and through the ends of the E-block actuator arms. Passage of the ball spreads the metal of the flexure against the walls of the holes in the actuator arms to stake the HGAs in place. This staking operation is extremely prone to error. Error rates increase as the number of actuator areas of the E-block increases. It is extremely difficult to ensure that each of the HGAs is securely fastened to its actuator arm with this method. In addition, if one of the HGAs is not securely fastened to its actuator arm of the E-block, the entire E-block with 14 heads (HGAs) could be discarded. This can get very expensive. Therefore, there is a need for a more uniform assembly technique of HGAs to actuator arms that reduces the likelihood and consequence of defects in manufacturing and assembly.
Another problem with current hard disk drive construction techniques is that although the stack of hard disks is sequentially assembled on the drive motor hub, the actuator is separately assembled as a unit apart from the disk stack with all of the HGAs attached to the actuator arms. A spreader comb must then be inserted between the HGAs to allow the arms and HGAs to be inserted as a unit with the arms between the stacked disks. The comb is then removed and the actuator assembly installed or fastened to the frame of the drive apparatus. With present head and disk media assembly technology the release of the heads from the comb has to occur in the inner diameter of the disk. This operation is extremely delicate and often results in failed heads due to misalignment problems during installation.
Therefore there is a need for a more efficient and compact moving magnet actuator design for high performance hard disk drive systems that can be easily and accurately assembled and disassembled. In addition, there is a need for a high capacity high performance disk drive module having higher disk capacity in a more compact and efficient package.